ST. Thomas, USVI diesel oil spill soil remediation project case study

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Courtesy of Nordevco Associates Ltd.

The Problem
Staff at a major four-star resort outside St. Thomas in the US Virgin Islands spilled diesel fuel and kerosene during the transfer from a tanker truck to on-site storage tanks. Approximately 67.3 m3 of soil having an average concentration of 12,000 ppm was contaminated. Because there are no treatment facilities on the Island, the resort was facing significant costs to transport the contaminated soil to the mainland for treatment. Further complicating the issue was the fact that the contaminated soil had been excavated and moved to the side of a hill behind the resort to get it out of sight of clients and tourists.

Our Approach
Whereas the soil had been excavated, it was clear to Nordevco staff that the most cost effective and efficient approach would be to treat the soil in a wet cell using the BactiDomus Technology and a bioreactor. This would facilitate two-phase treatment — a primary treatment in the bioreactor and a secondary treatment in the wet cell. BactiDomus Technology product 401 was used for the primary treatment in the reactor and product 208 was used in the wet cell to initiate the breakdown of contaminants, making them more mobile and facilitating their transport to the bioreactor for the more active primary treatment.

Because the effectiveness of the treatment is based on the BactiDomus Technology, Nordevco staff determined that the most cost effective approach would be to build a simplified bioreactor on site with whatever materials were readily available locally. As a result, a bioreactor was designed using two 50 gallon oil drums welded together, a perforated metal product support plate, some ABS plastic residential plumbing fittings, two fifty gallon aquarium pumps and a small pump. When construction was completed, the bioreactor was loaded with product 401 and water was pumped from a sump in the wet cell to the reactor for treatment and then recirculated to the cell in a closed-loop.

The actual wet cell was built on the side of the hill using a locally available impermeable liner to line the cell and prevent the release of contamination. The cell was filled using a rubber-tired loader to prevent damaging the liner. Product 208 was spread over the contaminated soil. Following this, the cell was flooded and put into operation.

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